linux-kernel - [PATCH 2/6] NOMMU: Provide per-task stack usage through /proc for NOMMU

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Message-ID: <20091216235603.4310.71243.stgit@warthog.procyon.org.uk>
Date:	Wed, 16 Dec 2009 23:56:03 +0000
From:	David Howells <dhowells@...hat.com>
To:	torvalds@...l.org, akpm@...ux-foundation.org
Cc:	dhowells@...hat.com, vapier@...too.org, lethal@...ux-sh.org,
	linux-kernel@...r.kernel.org, uclinux-dev@...inux.org,
	David Howells <dhowells@...hat.com>,
	Mike Frysinger <vapier@...too.org>,
	Stefani Seibold <stefani@...bold.net>,
	Paul Mundt <lethal@...ux-sh.org>,
	Robin Getz <rgetz@...ckfin.uclinux.org>
Subject: [PATCH 2/6] NOMMU: Provide per-task stack usage through /proc for
	NOMMU

Make it possible to get the per-task stack usage through /proc on a NOMMU
system.  The MMU-mode routine can't be used because walk_page_range() doesn't
work on NOMMU.

It can be tested to show the stack usages of non-kernel-thread processes:

	# grep "Stack usage:" /proc/*/status | grep -v "0 kB"
	/proc/1/status:Stack usage:     2 kB
	/proc/57/status:Stack usage:    3 kB
	/proc/58/status:Stack usage:    1 kB
	/proc/59/status:Stack usage:    3 kB
	/proc/60/status:Stack usage:    5 kB
	/proc/self/status:Stack usage:  1 kB

I've only tested it with ELF-FDPIC, though it should work with FLAT too.

Signed-off-by: David Howells <dhowells@...hat.com>
Signed-off-by: Mike Frysinger <vapier@...too.org>
Cc: Stefani Seibold <stefani@...bold.net>
Cc: Paul Mundt <lethal@...ux-sh.org>
Cc: Robin Getz <rgetz@...ckfin.uclinux.org>
---

 fs/proc/array.c |   20 +++++++++++++++++---
 1 files changed, 17 insertions(+), 3 deletions(-)


diff --git a/fs/proc/array.c b/fs/proc/array.c
index 4badde1..c67251e 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -387,8 +387,7 @@ static inline unsigned long get_stack_usage_in_bytes(struct vm_area_struct *vma,
 	return ss.usage;
 }
 
-static inline void task_show_stack_usage(struct seq_file *m,
-						struct task_struct *task)
+static void task_show_stack_usage(struct seq_file *m, struct task_struct *task)
 {
 	struct vm_area_struct	*vma;
 	struct mm_struct	*mm = get_task_mm(task);
@@ -404,9 +403,24 @@ static inline void task_show_stack_usage(struct seq_file *m,
 		mmput(mm);
 	}
 }
-#else
+#else /* CONFIG_MMU */
+/*
+ * Calculate the size of a NOMMU process's stack
+ */
 static void task_show_stack_usage(struct seq_file *m, struct task_struct *task)
 {
+	unsigned long sp, base, usage;
+
+	base = task->stack_start;
+	sp = KSTK_ESP(task);
+
+#ifdef CONFIG_STACK_GROWSUP
+	usage = sp - base;
+#else
+	usage = base - sp;
+#endif
+
+	seq_printf(m, "Stack usage:\t%lu kB\n", (usage + 1023) >> 10);
 }
 #endif		/* CONFIG_MMU */
 

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